Many home entertainment devices not only include the capability to communicate with other devices in a home network but also include the ability to receive and/or process available media content from a plurality of sources, including a plurality of providers. The sources and providers may include, but are not limited to, satellite service, cable service, and free to home over the air terrestrial service. The services may operate in the same or different radio frequency (RF) ranges and may use the same or different transmission formats or protocols. The devices for receiving the services often include, but are not limited to, set-top boxes, gateways, televisions, home computers, and the like.
The operation of home entertainment devices is further complicated by the inclusion of home networking functions in the devices. Many of these devices use a home networking that shares the transmission medium such as cable with the incoming transmission system from the service providers. One such example is a multimedia over cable alliance (MOCA) home network system that operates from an RF signal provided by a cable in a frequency spectrum of 950 MHz-1050 MHz. The frequency spectrum, 950 MHz-1050 MHz, is unused by the other signal transmission systems. Examples of other signal transmission systems would be satellite down link frequencies from 1250 to 2150 MHz, broadcast television from 174 to 805 MHz and certain control frequencies from 2.3 to 2.4 MHz that are all contained in the same cable together with the MOCA RF signal.
Return loss is a measurement of how well the impedance of a load, including, for example, a filter that is driven from the signal contained in the cable, is matched to the characteristic impedance of the cable. The return loss is a number associated with a corresponding interface that is calculated from the reflection caused at the corresponding interface as a result of an impedance mismatch. The return loss is usually expressed as a ratio in decibels (dB).
The above mentioned filter may be a band-pass filter that passes the MOCA band signals and blocks the passage of signals at frequencies outside the MOCA band contained in the same cable along with the MOCA band signals. It may be desirable to avoid significant input return loss with respect to each signal that is contained in the same cable containing the MOCA band signals. Ideally, it may be desirable to provide a termination to the cable, for example, 75 ohms that matches the characteristic impedance of the cable for each signal within the frequency spectrum that is contained in the same cable including the MOCA band signals.
Typical practice is to design diplex, triplex or higher order L-C filters to divide the frequency bands. A corresponding termination such as a 75 ohm resistor would be coupled to an output of each of the filters. However, these filters are complex having a relatively large number of parts and require a corresponding filter for each of the frequency bands of the corresponding RF signals, not just for the RF signal at the band such as MOCA.
It is also well known to utilize a resistive network commonly referred to as “pad” for providing a terminating resistance over a wide frequency band. For example, a 6 dB pad will provide a −12 dB or better return loss S11 even in the extreme case in which an output terminal of the pad is either an open or short circuit. However, utilizing such a resistive pad downstream the input of a receiver would, undesirably, degrade the noise figure by 6 dB.
In carrying out an advantageous feature, the 6 dB pad is supplemented with relatively simple band-pass filter such that the desired frequency band, for example, of the MOCA home network system can be subjected, advantageously, to lower attenuation while RF signals at the range of frequencies that excludes the MOCA band are attenuated more and terminated with the resistive pad that provides improved impedance matching.